Our goal is to investigate the evolution and natural history of experimental atherosclerosis in the rat as induced by endothelial denudation of arterial linings via use of a balloon catheter. The results of single and multiple injuries will be studied in a new strain of genetically obese rat recently obtained in our laboratory. Such rats develop endogenous hyperlipidemia and spontaneous hypertension while their nonobese siblings are hypertensive but not hyperlipidemic. These two animal types along with normal Wistar rats (normotensive and normolipidemic) will be employed and this should permit us to evaluate the roles played by high blood pressure and by elevated plasma lipids, individually and in combination, in the genesis of atherosclerosis. Since both these items constitute high risk factors in the development of coronary heart disease, the results should have direct bearing on an important health problem in the human.